1. Field of the Invention
The present invention relates, in general, to methods and systems for cooling electronic components such as processors in servers and other computing devices, and, more particularly, to an enhanced heat sink assembly or device that can be attached to a heat generating surface of electronic components such as a processor to provide cooling based on the absorption refrigeration cycle in a passive manner, e.g., without use of compressors and motorized pumps.
2. Relevant Background
Removal of heat has become one of the most important challenges facing computer designers as failure to adequately cool devices can cause failure or operating problems. The rate of power dissipation from electronic components such as from processors (or CPUs) in high-performance server units continues to increase. For example, in servers and disk storage systems, the heat load per product footprint (or Watts/square feet) has grown from 200 to 300 W/ft2 to 1700 to 1900 W/ft2 in the past 18 years. Cooling technology has not been able to match this rapid pace of heat generation, and standard conduction and forced-air convection air cooling techniques are encountering fundamental limits in their ability to provide adequate cooling for such sophisticated electronic components. The reliability of an electronic system may suffer if high temperatures at hot spot locations are permitted to exist, e.g., a heat generating surface of a CPU or the like.
A typical cooling arrangement for a computer device such as a server will include a heat sink mounted such that its base is in heat conducting contact with an external surface of an electronic component. Fins extend up from the base and one or more fans are used to force cooling air to flow between the fins to eject heat from the heat sink and the component upon which the heat sink is mounted. Unfortunately, conventional thermal control schemes such as air cooling with fans and heat sinks and other cooling designs including thermoelectric cooling, heat pipes, and passive vapor chambers have either reached their practical application limits or are soon to become impractical for high-power electronic components such as for use in computer server units. For example, a conventional heat sink is limited by the space available to provide heat transfer fins and the number of fins and/or spacing may be limited by the amount of pressure drop that can be supported by the fans.
When standard cooling methods are no longer adequate, computer manufacturers are sometimes forced to reduce the speed of their processors to generate less heat so as to match power dissipation with the capacity of the available cooling devices. In other cases, computers are provided that are less reliable due to inadequate cooling. Manufacturers of electronic devices may also have to delay release of their new designs or products until a reliable cooling apparatus for removal of the heat from high heat dissipating electronic components is available for use. Additionally, thermal management of high heat flux server units necessitates the use of bulky fan and heat sink assembly units, which have limited the ability of computer server manufacturers to adequately increase the capacity of their systems due to imposed heat removal and space limitations.
The computer industry, in particular, is seriously challenged with thermal management of their high-performance and high-power electronic components. A number of attempts have been made to provide enhanced heat removal but none has been wholly successful. For example, attempts have been made to provide improved thermal paths (e.g., heat transfer paths) by reducing thermal resistance such as between a heat generating surface of a processor and heat transfer fins of a heat sink. Such designs of low thermal resistance have been used most often with fan-driven cooling air systems to try to maintain the junction between the heat sink and electronic component surface within an acceptable range such as 80 to 100° C. or the like (e.g., a few degrees above or below a desired operating temperature such as 85° C., 95° C., and so on). The electronic components may be high heat flux electronic components such as CPUs, ASICs, DIMMs, and the like. To date, the ever-increasing demand for processing speed is pushing the envelope of thermal management beyond what is attainable using traditional air cooling systems.
A major obstacle in efficient thermal management of high power computer servers, for example, is the presence of hot spots on the electronic components and inability of air cooling schemes in effectively removing heat from its point of generation. Additionally, reports indicate that in most data centers, over sixty percent of the overall data center energy demand is associated with cooling the information technology (IT) equipment. Moreover, it has been estimated that about seventy percent of the cost of managing servers in data centers is related to power and cooling and only twenty to thirty percent being related to the cost of the IT equipment itself. Therefore, designing a cooling system that effectively manages the thermal load with reliable performance and with reduced power consumption would represent a major breakthrough in the design of high performance servers.
There remains a need for improved methods and devices for removing heat from electronic components such as CPUs and the like. Preferably, such devices would require the same or less power than existing devices, would provide reliable service over the life of the electronic components, and would be sized and configured to fit within the footprint and/or size constrained spaces of today's and tomorrow's computing and other electronic devices.